John Plimmer wrote:
I recently got a Redsun RP2100, the users view of which I previously posted
on this group.
It has the facility to use rechargeable batteries, something of which I know
nothing about.
It will charge these batteries for twelve hours.
I want to use "D" cells but don't know which rechargeables to buy.
My local store can order me NiCad's or NiMH - I don't know anything about
that.
What's the difference?

Also there are different numbers like 1500 or 2500 which seems to mean how
long they hold the charge.
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About ten years ago I got a batch of heavy-duty Radio Shack Ni-Cads
rated at 5,000 mah. They were quite satisfactory but were a bit fiddly
to recharge correctly. I still have some of them. The larger capacity
was well worth their extra price. Many of the new NiMH batteries on the
matket today are just repackaged AA cells at 1500 or 2500 mah. A full D
cell would be rated at 11,000 mah and would last a very long time in a
radio. You might have to get a special charger, however, as the Redsun
seems to have a charger circuit for the smaller-capacity cells: maybe
you could just leave the higher-capacity cells in longer. The ni-cads
needed close attention: they developed "hairs" that had to be blasted
off with a 12-volt battery, they would develop a memory if not
discharged occasionally, and special chargers with "saw-tooth " wave
shapes were developed to get better efficiency. There is quite a bit of
literature on the care and feeding of Ni-Cads. They also self-discharge
in storage, so if you don't use the radio a lot, the cells go flat
anyway. If you use the radio a lot, and if you can handle the extra
cost, the 11,000 NiMH cells would be worth a look. Since I have far too
many radios, I stock them with cheap garden-variety D cells that hold
their charge in storage, and only use the NiMH cells in two often-used
portables.